Development Of Optical Surface Contamination Detection Device For Laser Communication Terminal And Effects Analysis

To meet people’s demands for high data rate, large-capacity communications, laser communication emerges. With high carrier frequency, laser communication is easy to realize the data rate of several Gbps, and its security is high. Therefore, it’s developed gradually. Nowadays, space networking becomes a new target. Thus, a large number of optical communication terminals need to be developed(user, ground, low orbit, middle orbit and high orbit). Communication performances of optical communication terminal are affected by many factors, the surface contamination is a major factor affecting performances of the optical system, and ultimately affects the working life of the satellite terminal. Therefore, it is necessary to estimate and detect contamination amount of the optical surface, and study pollution effects as well.At first, based on the basic principle of microscale contamination detection, 10 MHz aluminized quartz crystal microbalance(QCM) is developed, whose theoretical mass sensitivity is 10-9g/cm2. Calibration results of the apparatus show that: In actual measurement period, the time stability is good, which ensures the accuracy of pollution test; By introducing a reference crystal, it not only substantially eliminates the influence of environmental factors, but also reduces the requirement for the accuracy of temperature control; By directly measuring the frequencies of test crystal and reference crystal, it avoids the complexity of the system and the error caused by using a mixer; By absolute calibration experiment, the actual mass sensitivity is in the order of 10-8g/cm2 which can satisfy the actual needs, cost is low and it’s practical to be used; By 3D finite element method(3D-FEA), it shows that the applied voltage and the non-uniform pollution deposition have effects on quartz crystal mass sensitivity, which results in lower actual mass sensitivity compared to theoretical sensitivity.Then, through vacuum test, the paper confirms the effectiveness of the QCM being used to detect the amount of surface contamination. Based on outgassing model of organic non-metallic materials, pollution molecular transport model and molecular deposition model, a total pollution model is built and analysis preliminarily the pollution deposition process under vacuum test, providing foundation for prediction, prevention of optical surface contamination and material selection.Finally, the paper applies pollution model to Cassegrain optical antenna, analyzing the surface contamination deposition rate of primary and secondary mirror, while the light shield is the only pollution source. With coating function of Zemax, pollution effect is studied. Then simulating and analyzing the impact on optical power of the entire optical system with epoxy film of different thicknesses on primary and secondary mirror surfaces.